The present invention relates to a method for manufacturing a layer from an oxide ceramic superconductor material with a high transition temperature of a substance system containing metallic components and oxygen on a substrate by means of a chemical vapor deposition (CVD) process.
A method for depositing at least one layer from an oxide-ceramic superconductor material of a substance system with a high transition temperature containing metallic components and oxygen on a substrate is the subject matter of German Patent Application P 37 34 069.7 filed Oct. 8, 1987. The following process steps are thereby provided:
1) As parent materials, one provides respectively at least one vaporizable composition of each of the metallic components of the substance system,
2) each of these parent compositions is vaporized at a predetermined temperature and with a predetermined partial pressure and quantitatively regulated [dosed] by means of a carrier gas stream, so that the thus formed gas streams are subsequently united in a gas mixture, whereby one adjusts a metallic component ratio as needed to form the superconductor material,
3) to deposit the desired superconductor material, the conditions of reaction are adjusted using the energy supply for a reaction of or with the evaporated parent compositions.
According to a preferred specific embodiment of this method, at least one additional gaseous coreactant is directed to the gas mixture from the gas streams containing the parent composition, by means of a carrier gas, which can react with the evaporated parent compositions while forming the superconductor material. Superconductive metal oxide compositions are known which are based on a substance system containing metallic components and oxygen. They are distinguished by such high transition temperatures T.sub.c, that cooling is possible with liquid nitrogen of approximately 77 K at standard pressure. Y-Ba-Cu-O, Bi-Sr-Ca-Cu-O and Tl-Ba-Ca-Cu-O in particular are appropriate substance systems. Thin coatings or films from these materials can often be manufactured using special PVD (physical vapor distribution) processes such as, for example, coating by evaporation or sputtering. Moreover, experiments have already been carried out where coatings from these materials are deposited on to substrates by means of special CVD processes as well. Included among these is the process described in the patent application mentioned above.
According to this proposed method, as parent materials, at least one vaporizable composition of each of the metallic components of the substrate system is provided respectively. Chelate, preferably .beta.-diketonate, is especially suited for use as a parent composition of the metallic components. Each of these three parent compositions is then vaporized at a predetermined temperature and a predetermined partial pressure. The thus formed gas streams are then quantitatively regulated by means of a special carrier gas stream, for example of argon, and united into a gas mixture, so that one obtains the metallic component ratio which is needed to form the superconductor material. At least one additional gaseous coreactant, which can react with the evaporated parent compositions thereby forming the superconductor material, can be directed by means of a carrier gas stream to the gas mixture. For this purpose, vaporized (gaseous) water or oxygen gas are proposed as especially suited coreactants. To deposit the desired superconductor material, the conditions of reaction are finally adjusted through the energy supply for a reaction of or with the gaseous parent compositions and the coreactant. The energy supply can be provided in particular by increasing temperature. The deposition of the superconductor material can take place thereby in a reaction of or with the parent compositions and the coreactant, as a result of the hydrolysis of the parent compositions and dehydration of the thereby recovered hydroxide, or also as a result of the oxidation of the parent compositions.